This patent document relates to devices and techniques for particle composition analysis.
Various methods for particle analysis involve impaction and collection of airborne particles on a filter, and subsequent analysis. The analysis can be achieved in various ways, including chemical digestion and subsequent analysis by atomic absorption spectroscopy, inductively-coupled plasma optical emission spectroscopy, inductively-coupled plasma mass spectrometery, measurements with a scanning electron microscope, or measurements with a transmission electron microscope.
Real-time particle composition analysis can be achieved by using an aerosol mass spectrometer which analyzes bulk particles, and an aerosol time-of-flight mass spectrometer which analyzes single particles. In either case, particles are drawn through an orifice or aerosol lens into a particle beam, in which they are partially or completely vaporized using any one of several methods. Ions from the vaporization process are detected to infer the composition of particles from the ion fingerprint. Laser-induced breakdown spectroscopy can also be used to measure aerosols, either singly or in bulk. In these instruments, analysis can be real-time or nearly real-time. Many implementations of such instruments tend to be expensive and physically large, and complex.
Researchers at the National Institutes of Occupational Safety and Health attracted particles to a charged pin, and performed laser-induced breakdown spectroscopy to create a plasma to vaporize the attracted particles, exciting atomic emission that provides information about the composition of the particles. This approach can provide simplicity of concentrating the particles and good analysis results. The approach does rely upon a laser, which may present optical hazards, requires maintenance by skilled technicians, and other complications, and also may lack electrical and efficient aerodynamic focusing.